Mr Evans was clerk for a record 21 years, from February 17, 1988 to December 4, 2009. Although he has been ill since his retirement, friends have described his death as unexpected.

He started off his career at Parliament House as a trainee at the Parliamentary Library, moving up through the ranks from deputy usher of the black rod to becoming clerk.

He was responsible for setting up the Senate Procedure Office - the same office that schooled the likes of Palmer United Party senators and Ricky Muir on their arrival to Canberra on the ins and outs of debate and voting.

He called, in a retirement essay published in Crikey, for parliamentary reform to counter against fumbled executive responses to the great crises of our time.

Leader of the Government in the Senate Eric Abetz said Mr Evans was a strong defender of parliamentary process and of the Senate's role as a house of review.

Senator Abetz offered condolences to Mr Evan's family and praised him for being one of the "most succinct writers" he knew, with some of the best knowledge of the procedures and precedents of the Senate.

Mr Abetz said Mr Evans gave more than 40 years of his life to the Senate.

"He was a fearless defender of its powers and practices and will be remembered as one of the significant parliamentary officers of his generation, not only of Australia but of all the parliamentary democracies," Senator Abetz said.

Leader of the Opposition in the Senate Penny Wong has offered her condolences to Mr Evans's family and dubbed him "a champion of the Senate and our parliamentary democracy" on his passing.